Deutsche Thomson-Brandt Gmbh

Thomson Licensing

Thomson Licensing S.a.

Veit Armbruster

Herbert Peusens

Alfred Selz

Claus Muschallik

Gerhard Maier

Klaus Clemens

Reinhard Sauter

Gerald Dullberg

Gerd Siegel

Helmut Hirt

Stefan Stalf

Ali Dener

The circuit arrangement comprises a tuner with a control amplifier and a mixer connected downstream, and an automatic gain control. The automatic gain control contains a weighting filter, which is connected to the output of the mixer, upstream of an intermediate frequency filter, and which supplies the control signal for the control amplifier of the tuner via a detector. The weighting filter has, in particular, a passband, which corresponds to the passband of the intermediate frequency filter and at least partly encompasses at least one or two adjacent program channels. As a result of this, the control amplifier is better tuned under difficult reception conditions, since, by means of the weighting filter, adjacent channels, relative to the passband of the intermediate frequency filter, are also concomitantly included in the control signal.

Automatic gain control for a tuner

A circuit for breaking a signal path has not only a switching means but also a low-pass or bandpass filter whose frequency characteristic is switchable or bypassable. The insulation between the input and the output when the switching means is open, which decreases with frequency in the case of ordinary switching means, is compensated for by the filter which is then connected. In one embodiment of the circuit, an out-of-band signal is applied to the circuit in addition to the useful signal. The out-of-band signal is intended to be supplied permanently to an evaluation circuit, regardless of the switching position of the switching means. To this end, the out-of-band signal is tapped off downstream of the filter, and the filter is designed such that the out-of-band signal can pass through the filter. In the case of a circuit for selecting one of two inputs, at least one of the inputs is provided with a switchable or bypassable filter, and the switching means is a selection means. Even when the input is not selected, an out-of-band signal is forwarded to an evaluation circuit. To this end, the out-of-band signal, as described above, is tapped off downstream of the filter and upstream of the selection means.

Signal input circuit

A single conversion tuner suitable for receiving RF signals having different requirements as to selectivity, linearity and image rejection is presented. Tuners of this kind are particularly useful for digital terrestrial as well as cable reception, where different modulation schemes require very high image rejection ratios on one hand and high linearity or pass band flatness on the other hand. The inventive tuner features a double-tuned tuneable filter in combination with an image reject mixer. The double-tuned filter provides excellent pass band flatness, while the image reject mixer provides a high intrinsic image rejection. The image rejection ratio of the combination of image reject mixer and tuneable filter is very high and fulfils the requirements of commonly used modulation schemes such as 8VSB, while the pass band flatness is compliant with the requirements for modulation schemes such as QAM.

Single conversion tuner

In apparatuses (1, 2, 3) controlled or operated via an IC bus, it may be necessary to take measures to suppress interference signals at the data signal input/output of the respective apparatus without impairing the data transport at the same time. The data line at the data signal input/output contains an RC element, in the form of a low-pass filter, with a diode connected in parallel with the RC element, the low-pass filter action allowing the arrangement to be used to suppress interference signals acting on the data signal input/output, and, secondly, the transmissive action of the diode meaning that the arrangement does not impair a data signal leaving the data signal input/output.

Data bus

According to the invention a digital signal path includes a first filter and an analog signal path includes a second filter. For analog reception both filters are connected in cascade, the first filter aiding the second filter in achieving a desired selectivity. Additional selection devices are obviated. Preferably the filters are surface acoustic wave filters.

Amplifier circuit arrangement for alternatively processing a digital or an analog signal

In an OFDM system, the so-called self-noise component, which represents that noise component of the respective carrier which is caused by the carrier itself and is mapped onto itself, can be estimated and corrected by shifting all the carriers back in the receiver by multiplication by a factor which is determined by averaging. The so-called external-noise component, which is caused by adjacent carrier interference from the so-called leakage effect of the Fast Fourier transform (FFT,) used in the receiver for demodulation cannot be corrected using this method. In addition to the demodulation FFT, a further FFT (FFT,) is used in the receiver to estimate the self-noise component (&psgr;,). The estimated self-noise component is used to reproduce the orthogonality between the carriers by correction before the demodulation FFT, to thereby prevent crosstalk. The additional FFT (FFT,) may have a shorter length than the demodulation FFT (FFT,), so that the additional complexity is negligible.

Method and circuit arrangement for the correction of phase and/or frequency errors in digital multicarrier signals

Method and circuit arrangement for improving carrier separation for the

Components for analog or digital input signals are in each case connected by switchable means to a controllable oscillator. The switch condition of the switchable means is set automatically and/or manually as a function of the input signal.

Switchable circuit for processing and demodulating digital and analog

Terrestrial and satellite television reception tuner

A filter circuit having an amplifier stage, an upstream filter and a downstream bandpass filter. The filter includes, inter alia, a rejection circuit tuned to an intermediate frequency and a series circuit, tuned to an image frequency and formed by a capacitor and a .lambda./4 coaxial stub. The inductance formed by the coaxial stub is shared by the series circuit and the rejection circuit.

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St. Georgen, Germany

Veit Armbruster